The invention pertains to the field of manufacturing ironless, self-supported rotors for electric motors.
It is known to manufacture tubular-shaped ironless rotors by winding onto a form a length of insulated wire in a non-overlapping configuration, separating the so formed length from the form and deforming the so-formed length of wire into a substantially flat configuration and thereafter joining the ends of the flattened structure to form a tubular-shaped coil. Such a method results in a coil having two layers of wire and accordingly a thickness of double the diameter of the wire. This known method is applicable only to wires of relatively heavy gauge.
According to another known method, an insulated wire is wound on a flat magnetic core, which is thereafter bent into a tubular-shaped configuration. The coil is composed of individual or distinct groups of windings, and in each group of windings the individual layers have a decreasing number of turns, which leads to a trapezoidal configuration as to the cross-section of each group. Thus, any disired length of a bandlike coil structure may be cut intermediate adjacent groups of windings without separating more than one winding. This known method does not lead to an ironless rotor. Besides, the windings on the core lie in a plane intersecting the coil axis.